The specific aim of this study is to test the hypothesis that white matter ischemia is a major contributor to neurological deficit following spinal cord injury. Experiments will be performed using the hydrogen clearance method to measure acute blood flow changes following spinal cord injury in the cat. Chronic experiments will be performed in which the neurological status of the cats will be determined. Both the chronic and the acute series will test several pharmacologic manipulations which may either improve or worsen blood flow. The acute effects on blood flow of the treatment will be compared with the chronic effects on neurological recovery. If a relationship between blood flow and neurologic outcome is found then a strong basis for inferring causal relationship will be established. If little or no relationship between them is found, then a major portion of the secondary injury hypothesis of spinal cord trauma must be reconsidered. The long term objective of this study is to provide evidence for the factors producing neurologic deficits and to develop a reationale for treatment of the injuries.